NEW STRATEGIES FOR ENANTIOSELECTIVE SYNTHESES OF 1-ALKYL-1,2,3,4-TETRAHYDROISOQUINOLINES AND 1,4-DIALKYL-1,2,3,4-TETRAHYDROISOQUINOLINES - DIASTEREOSELECTIVE ADDITIONS OF NUCLEOPHILES AND ELECTROPHILES TO ISOQUINOLINE MEDIATED BY AN EASILY RESOLVED AND RECYCLED CHIRAL TRANSITION-METAL AUXILIARY
Gb. Richteraddo et al., NEW STRATEGIES FOR ENANTIOSELECTIVE SYNTHESES OF 1-ALKYL-1,2,3,4-TETRAHYDROISOQUINOLINES AND 1,4-DIALKYL-1,2,3,4-TETRAHYDROISOQUINOLINES - DIASTEREOSELECTIVE ADDITIONS OF NUCLEOPHILES AND ELECTROPHILES TO ISOQUINOLINE MEDIATED BY AN EASILY RESOLVED AND RECYCLED CHIRAL TRANSITION-METAL AUXILIARY, Journal of the American Chemical Society, 115(25), 1993, pp. 11863-11873
The chiral rhenium isoquinoline complex [(eta5-C5H5)Re(NO)(PPh3)(iso-N
C9H7)]+ TfO- (1) and (CH3)3-SiCH2Li give the addition product eta5-C5H
5)Re(NO)(PPh3)(NCH=CHC(CH)4CCHCH2Si(CH3)3) (2) in 71% yield as a 94:6
SS,RR/SR,RS diastereomer mixture. Similar reactions with RMgX (R = (CH
3)2CH, CH3CH2, C6H5CH2, CH3(CH2)2, CH3, CH3(CH2)3) give analogous addu
cts (3-8) as 89-82:11-18 diastereomer mixtures. Reactions of 2 and ROT
f (R = H/D, (CH3)3SiCH2, CH3) give alkyl-1,4-dihydroisoquinoline compl
exes -C5H5)Re(NO)-(PPh3)(N=CHCHRC(CH)4CCHCH2Si(CH3)3)]+ TfO- in 84-72%
yields as 94:6 diastereomer mixtures. Related complexes are prepared
from 3-5 and HOTf. These react with NaBH4/CH3OH to give alkyl-1,2,3,4-
tetrahydroisoquinoline complexes, which are in turn treated with (CH3C
H2)4N+ CN- to give (eta5-C5H5)Re(NO)(PPh3)(CN) (17) and the title comp
ounds. A reaction sequence starting with (+)-(S)-1 and (CH3)3SiCH2Li y
ields (+)-(SS)-NHCH2-CH(CH2Si(CH3)3)C(CH)4CCHCH2Si(CH3)3 (84% overall,
88% ee) and (+)-(S)-17(82%, >98% ee). Other optically active alkyl te
trahydroisoquinolines are similarly prepared. Complexes 17 and (+)-(S)
-17 are converted to (eta5-C5H5)Re(NO)(PPh3)(CH3) (CH3OTf/NaBH4; 88-53
%) and thence to 1 or (+)-(S)-1 (92-74%, >98% ee). A crystal structure
and other data confirm the configurations assigned to the preceding c
ompounds.